The antigens of L. monocytogenes (LM) against which CMI is directed will be characterized chemically and immunologically. Attempts will be made to immunize mice against live challenge with LM by means of listeria antigens in combination with immunopotentiating agents. Having developed an effective method of immunization against mouse malaria, the character of this immune response will be analyzed. In particular the relative importance of CMI and humoral antibodies will be explored and the specificity of the response will be investigated. The nature of the CMI response to murine leprosy will be investigated with particular emphasis on the mechanism by which this response is specifically subverted by homologous antigen. Other mycobacterial infections will also be studied to see if suppression of CMI can be achieved in models in which CMI is sustained at high levels for long periods.